Salt Sensitivity Research Articles

Efficacy of the calcium channel blocker amlodipine in the treatment of salt-sensitive hypertension in patients with different genetic status

Aim. To study the effectiveness of the calcium channel blocker amlodipine in the treatment of salt-sensitive hypertension (HTN) and compare it with the genotypes of patients.Material and methods. The study involved 96 patients aged 42,7±5,2 years. There were following inclusion criteria: diagnosis — grade 1, stage 1 hypertension with low risk of cardiovascular events (CVEs). Before inclusion in the study, patients had not taken regular antihypertensive therapy for 3 months. Next, all patients underwent assessment of salt sensitivity of blood pressure according to the M. H. Weinberger method and, based on it, the participants were divided into salt-sensitive and salt-resistant. Regardless of the result, all patients were recommended to have a low-salt diet of 3-5 g/day, with subsequent 24-hour ambulatory blood pressure monitoring (ABPM) during the diet. In patients with ineffective diet, amlodipine was prescribed on day 26 at a dose of 2,5-5 mg once a day. The effectiveness of the drug was assessed by repeated ABPM. In addition, a genetic study was performed on 4 polymorphic variants of the genes AGT (T704C), AGT (C521T), AGTR1 (A1166C), AGTR2 (G1675A), ADD1 (G1378T), CYP11B2 (C344T), GNB3 (C825T), NOS3 (T786C), NOS3 (G894T), to determine their association with the effectiveness of a low-salt diet and amplodipine therapy.Results. In patients with grade 1, stage 1 hypertension with low risk of CVEs, the effectiveness of a low-salt diet and amlodipine monotherapy at a dose of 2,55 mg/day was revealed. The results of the study were confirmed by achieving target values of office blood pressure and ABPM. In hypertensive patients not sensitive to salt, amlodipine monotherapy was ineffective. The genotyping revealed a relationship between antihypertensive therapy with amlodipine in salt-sensitive patients and carriage of the GG polymorphism of the AGTR2 gene.Conclusion. The effectiveness of amlodipine and a low-salt diet in salt-sensitive patients with grade 1 hypertension, stage 1, low risk of CVEs with carriage of the GG genotype of the AGTR2 gene.

T helper cell polarity determines salt sensitivity and hypertension development.

High-salt intake is known to induce pathogenic T helper (Th) 17 cells and hypertension, but contrary to what is known, causes hypertension only in salt-sensitive (SS) individuals. Thus, we hypothesized that Th cell polarity determines salt sensitivity and hypertension development. Cultured splenic T cells from Dahl SS and salt-resistant (SR) rats subjected to hypertonic salt solutions were evaluated via ELISA, flow cytometry, immunocytochemistry and RT-qPCR. Seven-week-old SS and SR rats were fed a chow (CD) or high-salt diet (HSD) for 4 weeks, with weekly measurements of systolic blood pressure. The relaxation response of the aorta rings to the cumulative addition of acetylcholine was measured ex vivo. In these experimental animals, the Th cell polarity (Th17 and T regulatory [Treg]), the expression of Th17- or Treg-related genes, and the enrichment of the transcription factors RORγt and FOXP3 on the target gene promoter regions were determined via flow cytometry, RT-qPCR, and chromatin immunoprecipitation. Hypertonic salt solution induced Th17 and Treg cell differentiation in cultured splenic T cells isolated from SS and SR rats, respectively. HSD induced hypertension, endothelial dysfunction and proinflammatory Th17 cell differentiation only in SS rats. The enrichment of RORγt on the promoter regions of Il17a and Il23r increased their expression only in SS rats. Regardless of HSD, SR rats remained normotensive with Treg polarity, causing high Treg-related gene expressions (Il10, Cd25 and Foxp3). This study demonstrated that Th cell polarity determines salt sensitivity and drives hypertension development. SR rats were protected from HSD-associated hypertension via anti-inflammatory Treg polarity.

Regulation of human salt-sensitivite hypertension by myeloid cell renin-angiotensin-aldosterone system.

Introduction: Salt sensitivity of blood pressure is a phenomenon in which blood pressure changes according to dietary sodium intake. Our previous studies found that high salt activates antigen presenting cells, resulting in the development of hypertension. The mechanisms by which salt-induced immune cell activation is regulated in salt sensitivity of blood pressure are unknown. In the current study, we investigated dietary salt-induced effects on the renin-angiotensin-aldosterone system (RAAS) gene expression in myeloid immune cells and their impact on salt sensitive hypertension in humans. Methods: We performed both bulk and single-cell sequencing analysis on immune cells with in vitro and in vivo high dietary salt treatment in humans using a rigorous salt-loading/depletion protocol to phenotype salt-sensitivity of blood pressure. We also measured plasma renin and aldosterone using radioimmunoassay. Results: We found that while in vitro high sodium exposure downregulated the expression of renin, renin binding protein and renin receptor, there were no significant changes in the genes of the renin-angiotensin system in response to dietary salt loading and depletion in vivo. Plasma renin in salt sensitive individuals tended to be lower with a blunted response to the salt loading/depletion challenge as previously reported. Discussion: These findings suggest that unlike systemic RAAS, acute changes in dietary salt intake do not regulate RAAS expression in myeloid immune cells.

CdWRKY2 transcription factor modulates salt oversensitivity in bermudagrass [Cynodon dactylon (L.) Pers.

Common bermudagrass [Cynodon dactylon (L.) Pers.] has higher utilization potential on saline soil due to its high yield potential and excellent stress tolerance. However, key functional genes have not been well studied partly due to its hard transformation. Here, bermudagrass "Wrangler" successfully overexpressing CdWRKY2 exhibited significantly enhanced salt and ABA sensitivity with severe inhibition of shoot and root growth compared to the transgenic negative line. The reduced auxin accumulation and higher ABA sensitivity of the lateral roots (LR) under salt stress were observed in CdWRKY2 overexpression Arabidopsis lines. IAA application could rescue or partially rescue the salt hypersensitivity of root growth inhibition in CdWRKY2-overexpressing Arabidopsis and bermudagrass, respectively. Subsequent experiments in Arabidopsis indicated that CdWRKY2 could directly bind to the promoter region of AtWRKY46 and downregulated its expression to further upregulate the expression of ABA and auxin pathway-related genes. Moreover, CdWRKY2 overexpression in mapk3 background Arabidopsis could partly rescue the salt-inhibited LR growth caused by CdWRKY2 overexpression. These results indicated that CdWRKY2 could negatively regulate LR growth under salt stress via the regulation of ABA signaling and auxin homeostasis, which partly rely on AtMAPK3 function. CdWRKY2 and its homologue genes could also be useful targets for genetic engineering of salinity-tolerance plants.

Matrix metalloproteinase-9 regulates afferent arteriolar remodeling and function in hypertension-induced kidney disease

This study tested if matrix metalloproteinase (MMP)-9 promoted microvascular pathology that initiates hypertensive (HT) kidney disease in salt-sensitive (SS) Dahl rats. SS rats lacking Mmp9 (Mmp9-/-) and littermate control SS rats were studied after one week on a normotensive 0.3% sodium chloride (Pre-HT SS and Pre-HT Mmp9-/-) or a hypertension-inducing diet containing 4.0% sodium chloride (HT SS and HT Mmp9-/-). Telemetry-monitored blood pressure of both the HT SS and HT Mmp9-/- rats increased and did not differ. Kidney microvessel transforming growth factor-beta 1 (Tgfb1) mRNA did not differ between Pre-HT SS and Pre-HT Mmp9-/- rats, but with hypertension and expression of Mmp9 and Tgfb1 increased in HT SS rats, along with phospho-Smad2 labeling of nuclei of vascular smooth muscle cells, and with peri-arteriolar fibronectin deposition. Loss of MMP-9 prevented hypertension-induced phenotypic transformation of microvascular smooth muscle cells and the expected increased microvascular expression of pro-inflammatory molecules. Loss of MMP-9 in vascular smooth muscle cells invitro prevented cyclic strain-induced production of active TGF-β1 and phospho-Smad2/3 stimulation. Afferent arteriolar autoregulation was impaired in HT SS rats but not in HT Mmp9-/- rats or the HT SS rats treated with doxycycline, an MMP inhibitor. HT SS but not HT Mmp9-/- rats showed decreased glomerular Wilms Tumor 1 protein-positive cells (a marker of podocytes) along with increased urinary podocin and nephrin mRNA excretion, all indicative of glomerular damage. Thus, our findings support an active role for MMP-9 in a hypertension-induced kidney microvascular remodeling process that promotes glomerular epithelial cell injury in SS rats.

Lymphatics: Future Perspectives Unrealized Potential

Proposed fundamental laws of biology and a model of health and disease underscore the importance of the lymphatic system. The lymphatics are responsible for two of the laws of biology and the fulcrum of health and disease balancing regeneration with degeneration through the immune system. It is responsible for protection from the environment and repair of senile and damaged tissue. Life is constantly bombarded by forces that increase entropy. Lymphatics provide negative entropy to maintain health. Lymphatics help maintain cellular homeostasis removing products of metabolism. Using these principles, the role of lymphatics is investigated in salt sensitivity hypertension, cardio-renal system, the new pillar of heart failure and kidney disease—Sodium-Glucose Transport Protein 2 (SGLT2) Inhibitors, and brain diseases. The realization of organ lymphatics in maintenance of health and disease opens the avenue to new therapeutics. This is the unrealized potential of lymphatic study.

P23-037-23 Association of Dietary Habits With Salt Sensitivity of Blood Pressure in Gannan Tibetans Varies With Blood Pressure

P23-037-23 Association of Dietary Habits With Salt Sensitivity of Blood Pressure in Gannan Tibetans Varies With Blood Pressure

Reservoir Sensitivity Analysis of Tight Sandstone and Its Controlling Factors: A Case Study from Chang 4+5 to Chang 6 Reservoirs in N 212 Well Block of Nanniwan Oilfield, Ordos Basin

Reservoir sensitivity can lead to the physical or chemical reactions to block the pore throat. It is helpful for reducing the damage on tight sandstone reservoir to study the reservoir sensitivity and its controlling factors. This paper mainly focuses on the tight sandstone of the Chang 4+5 and Chang 6 reservoirs of the Yanchang Formation in the Nanniwan Oilfield, Ordos Basin. The reservoir sensitivity characteristics were evaluated through the core sensitivity experiment after the petrological and petrophysical analysis and pore structure study. The influencing factors on tight sandstone reservoir sensitivity were discussed from several aspects, such as clay mineral composition, porosity, permeability, and pore structure. The results show that the rock type of the Chang 4+5 and Chang 6 reservoirs in the N 212 well block of the Nanniwan Oilfield is mainly arkose, with the mean porosity of 11.2% and 8.45% and the mean permeability of 0.35 × 10 − 3 μm2 and 0.44 × 10 − 3 μm2, respectively. The clay mineral components mainly include chlorite and illite/smectite. Both the two reservoirs are characterized by moderate to weak velocity sensitivity, moderate to weak water sensitivity, moderate to strong salt sensitivity, weak acid sensitivity, and moderate to weak alkali sensitivity. In specific, the Chang 4+5 reservoir is stronger in velocity and salt sensitivities, while it is weaker in water, acid, and alkali sensitivities than those of the Chang 6. The major controlling factors on reservoir sensitivity are clay mineral component, petrophysical property, and pore structure. Among these, the velocity sensitivity displays the positive correlation with pore structure, porosity, and permeability. The water sensitivity will become strong with the increase of the volume content of illite/smectite, but weak with the getting better of pore structure. The acid sensitivity is positively correlated with the volume content of chlorite but is negatively correlated with pore structure. With the getting better of pore structure, the salt sensitivity and alkali sensitivity will become strong and weak, respectively. The research results can be as the guidance for the tight sandstone reservoir protection in the study area and the adjustment and optimization of the regional reservoir development scheme.

Hemodynamic Parameters in Students with Different Thresholds of Salt Sensitivity and Type of Autonomic Tone: An Observational Cohort Study

Background. Hemodynamic parameters are interrelated with both the threshold of salt sensitivity and the type of initial autonomic tone. Available data on such relationships are insufficient. Objective — to identify the hemodynamic parameters and features in students with different thresholds of salt sensitivity and types of autonomic tone.Methods. The study enrolled 174 second-year students of Kirov State Medical University, aged 18–23, who gave consent to the survey. The study was conducted over a period of four months and included two stages. At the first stage, all participants were evaluated for the threshold of salt sensitivity. According to the results, two groups were formed: group A — students with a normal threshold of salt sensitivity (n = 127); group B — students with a high threshold of salt sensitivity (n = 39). In the formed groups, a comparative analysis of hemodynamic parameters was carried out. At the second stage of the study, after assessing the initial autonomic tone, three groups were identified: group 1 (n = 40) — students with equilibrium of the sympathetic and parasympathetic systems (normotension); group 2 (n = 104) — students with dominating parasympathetic regulation of the heart rhythm (vagotonia); group 3 (n = 22) — students with dominating sympathetic regulation of the heart rhythm (sympathicotonia). Hemodynamic parameters were also studied in these groups. Statistical data processing was carried out using Statistica Advanced 10 for Windows RU. The differences between the comparison groups were assessed using parametric Student’s t-test and non-parametric Mann-Whitney U-test.Results. A high threshold of salt sensitivity was revealed in 23% of students. When comparing hemodynamic parameters in the groups, it was found that students with high thresholds of salt sensitivity had significantly higher values of systolic blood pressure, diastolic blood pressure, pulse pressure and average hemodynamic pressure than students with a low threshold. Differences in hemodynamics in students may be caused by differences in the original autonomic tone. Thus, students with vagotonia, if compared to those with normotension, have significantly lower values of heart rate, cardiac minute output, double product, and circulatory efficiency ratio, but a higher value of the peripheral vascular resistance. Students with sympathicotonia have statistically higher heart rate, cardiac minute output, and double product values.Conclusion. The assessment of hemodynamic parameters in healthy young people in relation to the threshold of salt sensitivity and the initial autonomic tone enables the risk factors for the development of hypertension to be assessed, prehypertension (high normal blood pressure) to be identified, and preventive programs aimed at reducing the number of diseases of the cardiovascular system to be developed.

The damaging duo: Obesity and excess dietary salt contribute to hypertension and cardiovascular disease.

Hypertension is a primary risk factor for cardiovascular disease. Cardiovascular disease is the leading cause of death among adults worldwide. In this review, we focus on two of the most critical public health challenges that contribute to hypertension-obesity and excess dietary sodium from salt (i.e., sodium chloride). While the independent effects of these factors have been studied extensively, the interplay of obesity and excess salt overconsumption is not well understood. Here, we discuss both the independent and combined effects of excess obesity and dietary salt given their contributions to vascular dysfunction, autonomic cardiovascular dysregulation, kidney dysfunction, and insulin resistance. We discuss the role of ultra-processed foods-accounting for nearly 60% of energy intake in America-as a major contributor to both obesity and salt overconsumption. We highlight the influence of obesity on elevated blood pressure in the presence of a high-salt diet (i.e., salt sensitivity). Throughout the review, we highlight critical gaps in knowledge that should be filled to inform us of the prevention, management, treatment, and mitigation strategies for addressing these public health challenges.

Functional NADPH oxidase 2 in T cells amplifies salt-sensitive hypertension and associated renal damage.

Infiltrating T cells in the kidney amplify salt-sensitive (SS) hypertension and renal damage, but the mechanisms are not known. Genetic deletion of T cells (SSCD247-/-) or of the p67phox subunit of NADPH oxidase 2 (NOX2; SSp67phox-/-) attenuates SS hypertension in the Dahl SS rat. We hypothesized that reactive oxygen species produced by NOX2 in T cells drive the SS phenotype and renal damage. T cells were reconstituted by adoptively transferring splenocytes (∼10 million) from the Dahl SS (SS→CD247) rat, the SSp67phox-/- rat (p67phox→CD247), or only PBS (PBS→CD247) into the SSCD247-/- rat on postnatal day 5. Animals were instrumented with radiotelemeters and studied at 8 wk of age. There were no detectable differences in mean arterial pressure (MAP) or albuminuria between groups when rats were maintained on a low-salt (0.4% NaCl) diet. After 21 days of high-salt diet (4.0% NaCl), MAP and albuminuria were significantly greater in SS→CD247 rats compared with p67phox→CD247 and PBS→CD247 rats. Interestingly, there was no difference between p67phox→CD247 and PBS→CD247 rats in albuminuria or MAP after 21 days. The lack of CD3+ cells in PBS→CD247 rats and the presence of CD3+ cells in rats that received the T cell transfer demonstrated the effectiveness of the adoptive transfer. No differences in the number of CD3+, CD4+, or CD8+ cells were observed in the kidneys of SS→CD247 and p67phox→CD247 rats. These results indicate that reactive oxygen species produced by NOX2 in T cells participates in the amplification of SS hypertension and renal damage.NEW & NOTEWORTHY Our current work used the adoptive transfer of T cells that lack functional NADPH oxidase 2 into a genetically T cell-deficient Dahl salt-sensitive (SS) rat model. The results demonstrated that reactive oxygen species produced by NADPH oxidase 2 in T cells participate in the amplification of SS hypertension and associated renal damage and identifies a potential mechanism that exacerbates the salt-sensitive phenotype.

Kir7.1 knockdown and inhibition alter renal electrolyte handling but not the development of hypertension in Dahl salt-sensitive rats.

High K+ supplementation is correlated with a lower risk of the composite of death, major cardiovascular events, and ameliorated blood pressure, but the exact mechanisms have not been established. Inwardly rectifying K+ (Kir) channels expressed in the basolateral membrane of the distal nephron play an essential role in maintaining electrolyte homeostasis. Mutations in this channel family have been shown to result in strong disturbances in electrolyte homeostasis, among other symptoms. Kir7.1 is a member of the ATP-regulated subfamily of Kir channels. However, its role in renal ion transport and its effect on blood pressure have yet to be established. Our results indicate the localization of Kir7.1 to the basolateral membrane of aldosterone-sensitive distal nephron cells. To examine the physiological implications of Kir7.1, we generated a knockout of Kir7.1 (Kcnj13) in Dahl salt-sensitive (SS) rats and deployed chronic infusion of a specific Kir7.1 inhibitor, ML418, in the wild-type Dahl SS strain. Knockout of Kcnj13 (Kcnj13-/-) resulted in embryonic lethality. Heterozygous Kcnj13+/- rats revealed an increase in K+ excretion on a normal-salt diet but did not exhibit a difference in blood pressure development or plasma electrolytes after 3 wk of a high-salt diet. Wild-type Dahl SS rats exhibited increased renal Kir7.1 expression when dietary K+ was increased. K+ supplementation also demonstrated that Kcnj13+/- rats excreted more K+ on normal salt. The development of hypertension was not different when rats were challenged with high salt for 3 wk, although Kcnj13+/- rats excrete less Na+. Interestingly, chronic infusion of ML418 significantly increased Na+ and Cl- excretion after 14 days of high salt but did not alter salt-induced hypertension development. Here, we found that reduction of Kir7.1 function, either through genetic ablation or pharmacological inhibition, can influence renal electrolyte excretion but not to a sufficient degree to impact the development of SS hypertension.NEW & NOTEWORTHY To investigate the role of the Kir7.1 channel in salt-sensitive hypertension, its function was examined using complementary genetic and pharmacological approaches. The results revealed that although reducing Kir7.1 expression had some impact on maintaining K+ and Na+ balance, it did not lead to a significant change in the development or magnitude of salt-induced hypertension. Hence, it is probable that Kir7.1 works in conjunction with other basolateral K+ channels to fine-tune membrane potential.

#4777 BLOOD PRESSURE RESPONSE TO A LOW SODIUM DIET IN NORMOTENSIVE SUBJECTS

Abstract Background and Aims The term salt sensitivity (SS) has been used to show an increase in BP in response to saline overload in both normotensive and hypertensive patients. Age, sex, and obesity have been proposed as predisposing factors. The objective of our work was to evaluate the response of office BP (OBP) and ambulatory BP (ABP) to changes in salt intake in healthy normotensive subjects. Method We analyzed 193 subjects who participated in the evaluation as potential kidney donors; none had a history of hypertension, diabetes, renal or cardiovascular disease. They received two consecutive standardized diets, one with 300 mEq and the other with 30 mEq of Na+/day. On the last day of each diet, a 24-h urine collection was obtained and an ambulatory BP monitor was placed for 24 h in the non-dominant arm, following recording of OBP. Data were expressed as mean and standard deviation (SD). Student's test and one-way ANOVA were used to compare means, values of p<0.05 were considered statistically significant differences. Results In the study group there were 120 females (62%) and 71 were salt sensitive (SS) (37%). The mean age was 46.9 ± 10 years (20 – 72) without significant gender differences (F = 46.7 ± 10 vs M = 47.3 ± 9 p = 0.704). The age of the salt sensitive (Ss) group was significantly higher than the salt resistant (Sr) (49.8 ± 9 vs 45.3 ± 10 p = 0.002). BMI was found to be increased (27.7 ± 4) without significant gender or incidence of SS differences. We found no association between gender and SS (p = 0.509). After the high sodium and before low sodium diets, the mean difference in urinary Na+ excretion was 165.2 ± 83 mEq/24h, significantly higher among men than women (201.6 ± 84 vs 142.3 ± 75 p = 0.0001). There were no differences based on SS. We did not find significant gender differences in the variation of OBP or ABP, with the changes in the diet. The mean reduction of systolic pressure OBP for the group was 6.13 ± 10 and of diastolic pressure OBP 0.35 ± 5 mmHg. In separate analysis, systolic and diastolic OBP drops were significantly higher in the Ss than in the Sr (9.69 ± 12 vs 2.57 ± 8 and 2.24 ± 7 vs – 0.95 ± 5 mmHg respectively, p = 0.001). The average reduction in systolic ABP was 7.13 ± 8 and in diastolic ABP 3.33 ± 5 mmHg. In separate group analysis we also observed a significantly greater reduction in Ss than in Sr (12.83 ± 7 vs 1.8 ± 5 and 6.56 ± 5 vs. 0.12 ± 3 mmHg respectively, p = 0.001). Conclusion In our study group, the reduction of both OBP and ABP following a low sodium diet in normotensive subjects depends on salt sensitivity and is independent of gender and body weight.

#4391 SALT SENSITIVITY AND HYPERTENSIVE NEPHROPATHY: A LINK TO BE DISCOVERED

Abstract Background and Aims Sodium sensitivity is defined as a change in blood pressure depending on sodium intake, which is present in about 30% of the adult population. According to blood pressure variation in salt load test we can classify the population in 3 categories: sodium sensitive (SS), sodium resistant (SR), inverse sodium sensitivity (ISS), based on, respectively, an increase, a non-significant variation or a decrease in the blood pressure values following the administration of sodium. It is reported that SS subjects have, independently from other risk factors, an increased risk of cardiovascular diseases. Moreover, SNPs located in genes related with Na+ metabolism, aldosterone synthesis and tubular sodium reabsorption in the kidney are related to salt sensitivity phenotype. The aim of this study is to analyze the relationship between sodium sensitivity and the development of hypertensive kidney damage in patients with primary hypertension. Method A cohort of 712 naïve hypertensive patients were classified for salt-sensitivity using acute saline test (NaCl 308 mEq / 2h / iv).127 patients (follow-up > 5 years- median 11) were selected for the present analysis (SS, n = 40; 0 SR, n = 46; RSS, n = 41). We analyzed annual decline of the eGFR (CDK-EPI) (Delta-eGFR) and development of microalbuminuria (MicrAlb) as renal outcome. Moreover, genetic polymorphism involved in salt sensitive hypertension has been investigated. Results No differences in Delta-eGFR was observed among the groups. However, SR subjects develop earlier microalbuminuria (P = .002) even with an adequate pressure control. Genotypes analysis revealed: polymorphism in CYP11B2 and NEDD4L to be protective against decline in eGFR. For microalbuminuria HSD3B1 and ADD3 seem to be a risk factors, whereas KL, PKD and TRPC6 polymorphism result protective factors. Conclusion Unexpectedly these finding suggests that SR patients are more at risk of developing hypertensive nephropathy than other groups of patients. Moreover genotypes associated with salt sensitivity play different and complex role in kidney damage in hypertension. Improvement in salt sensitivity testing and standardization will be needed to allow all this pathophysiological knowledge to be translated in a clinical setting.

Salinity changes the nitrification activity and community composition of comammox Nitrospira in intertidal sediments of Yangtze River estuary.

The newly discovered complete ammonia-oxidizing (comammox) Nitrospira has been identified in different environments, including coastal environments, where salinity is one of the most important factors for the abundance and activity of nitrifiers. Here, we demonstrate the effect of salinity on comammox Nitrospira, canonical ammonia-oxidizing bacteria (AOB), and ammonia-oxidizing archaea (AOA) in the intertidal sediments of the Yangtze River estuary based on microcosm experiments, DNA stable-isotope probing (DNA-SIP), and potential ammonium-oxidation rate (PAR) tests for different groups of ammonia oxidizers with selective inhibitors. During microcosm incubations, the abundance of comammox Nitrospira was more sensitive to increased salinity than that of other ammonia oxidizers. The results obtained with DNA-SIP heavy fractions showed that the dominant phylotype in clade A.2 (containing genes involved in the adaptation to haloalkaline environments) had high proportions in comammox Nitrospira community under both freshwater (0.06% salinity) and highly saline water (3% salinity) conditions. In contrast, another phylotype of clade A.2 (which lacks these genes) was dominant only under freshwater conditions. The PARs confirmed that comammox Nitrospira presented greater contributions to nitrification under freshwater conditions with a PAR of 4.37 ± 0.53 mg N·day-1·kg soil-1 (54%) than under saline water conditions with a PAR of 0.60 ± 0.94 mg N·day-1·kg soil-1 (18%). Moreover, AOA were specific to saline water conditions, whereas AOB were common under both freshwater and saline water conditions (44% and 52%, respectively). The present study provided evidence that salinity markedly affects the activity of comammox Nitrospira, and that the salt sensitivity of different phylotypes varies. IMPORTANCE Complete ammonia oxidation (comammox) is a newly discovered type of nitrification through which ammonia is oxidized to nitrate in an organism. Comammox Nitrospira were abundantly found in coastal ecosystems and demonstrated high community diversity. Changes in salinity are considered one of the most important factors to comammox Nitrospira in coastal ecosystems; however, reports on the correlation between them remain inconsistent. Therefore, it is critical to experimentally determine the influence of salinity on comammox Nitrospira in the coastal ecosystem. This study demonstrated a clear effect of salinity on the abundance, activity, and relative contribution of different ammonia oxidizers, especially for comammox Nitrospira. To the best of our knowledge, this is the first study demonstrating comammox Nitrospira activity at seawater salinities, implying the existence of a salt-tolerant type comammox Nitrospira, despite its activity being much lower than in freshwater conditions. The indicated correlation between the activity of specific comammox Nitrospira and salinity is anticipated to provide insights into the distribution of comammox Nitrospira and their potential contributions in estuaries and coastal ecosystems.

Silencing of PKG1 Gene Mimics Effect of Aging and Sensitizes Rat Vascular Smooth Muscle Cells to Cardiotonic Steroids: Impact on Fibrosis and Salt Sensitivity.

Background Marinobufagenin, NKA (Na/K-ATPase) inhibitor, causes vasoconstriction and induces fibrosis via inhibition of Fli1 (Friend leukemia integration-1), a negative regulator of collagen synthesis. In vascular smooth muscle cells (VSMC), ANP (atrial natriuretic peptide), via a cGMP/PKG1 (protein kinase G1)-dependent mechanism, reduces NKA sensitivity to marinobufagenin. We hypothesized that VSMCfrom old rats, due to downregulation of ANP/cGMP/PKG-dependent signaling, would exhibit heightened sensitivity to the profibrotic effect of marinobufagenin. Methods and Results Cultured VSMCfrom the young (3-month-old) and old (24-month-old) male Sprague-Dawley rats and young VSMCwith silenced PKG1 gene were treated with 1 nmol/L ANP, or with 1 nmol/L marinobufagenin, or with a combination of ANP and marinobufagenin. Collagen-1, Fli1, and PKG1 levels were assessed by Western blotting analyses. Vascular PKG1 and Fli1 levels in the old rats were reduced compared with their young counterparts. ANP prevented inhibition of vascular NKA by marinobufagenin in young VSMC but not in old VSMC. In VSMC from the young rats, marinobufagenin induced downregulation of Fli1 and an increase in collagen-1 level, whereas ANP blocked this effect. Silencing of the PKG1 gene in young VSMC resulted in a reduction in levels of PKG1 and Fli1; marinobufagenin additionally reduced Fli1 and increased collagen-1 level, and ANP failed to oppose these marinobufagenin effects, similar to VSMC from the old rats with the age-associated reduction in PKG1. Conclusions Age-associated reduction in vascular PKG1 and the resultant decline in cGMP signaling lead to the loss of the ability of ANP to oppose marinobufagenin-induced inhibition of NKA and fibrosis development. Silencing of the PKG1 gene mimicked these effects of aging.

Chemerin is resident to vascular tunicas and contributes to vascular tone.

The adipokine chemerin may support blood pressure, evidenced by a fall in mean arterial pressure after whole body antisense oligonucleotide (ASO)-mediated knockdown of chemerin protein in rat models of normal and elevated blood pressure. Although the liver is the greatest contributor of circulating chemerin, liver-specific ASOs that abolished hepatic-derived chemerin did not change blood pressure. Thus, other sites must produce the chemerin that supports blood pressure. We hypothesize that the vasculature is a source of chemerin independent of the liver that supports arterial tone. RNAScope, PCR, Western blot analyses, ASOs, isometric contractility, and radiotelemetry were used in the Dahl salt-sensitive (SS) rat (male and female) on a normal diet. Retinoic acid receptor responder 2 (Rarres2) mRNA was detected in the smooth muscle, adventitia, and perivascular adipose tissue of the thoracic aorta. Chemerin protein was detected immunohistochemically in the endothelium, smooth muscle cells, adventitia, and perivascular adipose tissue. Chemerin colocalized with the vascular smooth muscle marker α-actin and the adipocyte marker perilipin. Importantly, chemerin protein in the thoracic aorta was not reduced when liver-derived chemerin was abolished by a liver-specific ASO against chemerin. Chemerin protein was similarly absent in arteries from a newly created global chemerin knockout in Dahl SS rats. Inhibition of the receptor Chemerin1 by the receptor antagonist CCX832 resulted in the loss of vascular tone that supports potential contributions of chemerin by both perivascular adipose tissue and the media. These data suggest that vessel-derived chemerin may support vascular tone locally through constitutive activation of Chemerin1. This posits chemerin as a potential therapeutic target in blood pressure regulation.NEW & NOTEWORTHY Vascular tunicas synthesizing chemerin is a new finding. Vascular chemerin is independent of hepatic-derived chemerin. Vasculature from both males and females have resident chemerin. Chemerin1 receptor activity supports vascular tone.

SALT SENSITIVITY AND HYPERTENSIVE NEPHROPATHY: A LINK TO BE DISCOVERED

Objective: Sodium sensitivity is defined as a change in blood pressure depending on sodium intake, which is present in about 30% of the adult population. According to blood pressure variation in salt load test we can classify the population in 3 categories: sodium sensitive (SS), sodium resistant (SR), inverse sodium sensitivity (ISS), based on, respectively, an increase, a non-significant variation or a decrease in the blood pressure values following the administration of sodium. It is reported that SS subjects have, independently from other risk factors, an increased risk of cardiovascular diseases. Moreover, SNPs located in genes related with Na+ metabolism, aldosterone synthesis and tubular sodium reabsorption in the kidney are related to salt sensitivity phenotype. The aim of this study is to analyze the relationship between sodium sensitivity and the development of hypertensive kidney damage in patients with primary hypertension. Design and method: A cohort of 712 naïve hypertensive patients were classified for salt-sensitivity using acute saline test (NaCl 308 mEq / 2h / iv).127 patients (follow-up > 5 years- median 11) were selected for the present analysis (SS, n = 40; 0 SR, n = 46; RSS, n = 41). We analyzed annual decline of the eGFR (CDK-EPI) (Delta-eGFR) and development of microalbuminuria (MicrAlb) as renal outcome. Moreover, genetic polymorphism involved in salt sensitive hypertension has been investigated. Results: No differences in Delta-eGFR was observed among the groups. However, SR subjects develop earlier microalbuminuria (p = 0.002) even with an adequate pressure control. Genotypes analysis revealed: polymorphism in CYP11B2 and NEDD4L to be protective against decline in eGFR. For microalbuminuria HSD3B1 and ADD3 seem to be a risk factors, whereas KL, PKD and TRPC6 polymorphism result protective factors. Conclusions: Unexpectedly these finding suggests that SR patients are more at risk of developing hypertensive nephropathy than other groups of patients. Moreover genotypes associated with salt sensitivity play different and complex role in kidney damage in hypertension. Improvement in salt sensitivity testing and standardization will be needed to allow all this pathophysiological knowledge to be translated in a clinical setting

ABSENT VASOREACTIVE RESPONSE TO HIGH SODIUM INTAKE COINCIDES WITH SALT SENSITIVITY IN CKD PATIENTS

Objective: Chronic kidney disease (CKD) patients are advised to limit salt intake, because of its detrimental effects on blood pressure (BP) and albuminuria. The salt-sensitive BP response in CKD is classically attributed to impaired renal ability to excrete sodium (Na+) resulting in fluid overload. Yet, BP sensitivity to salt is also linked to vasodysfuction, and may even be fluid independent. We aimed to investigate which factor contributes to BP sensitivity to salt in CKD. Design and method: In this randomized crossover study, CKD patients (KDIGO stage G2-3A, proteinuria >0.5 g/d) and healthy controls (HC) followed a 7-day low sodium diet (LSD, <50mmol/d) and high sodium diet (HSD, >200mmol/d), respectively. After each diet, assessment of the hemodynamic profile included daytime BP (Mobil-O-Graph) and cardiac output (CO) measurements (using NexfinTM), by which SVR was calculated accordingly. Extracellular fluid volume (ECV) change was assessed with multi-frequency body impedance spectroscopy (FHCresenius). Results: We included 16 HC (median age 36.0 yrs) and 8 CKD patients (median age 49.5 yrs, and median (IQR) proteinuria 0.6 (0.5-1.1) g/d and plasma creatinine 144 (103 - 167) μmol/l. Dietary salt intervention was successful with median difference in urine Na+ excretion of 242.2 vs 224.6 mmol/day in HC and CKD respectively (p = 0.74). After HSD, the median (IQR) change in systolic BP of patients with CKD was 14 mmHg (4 - 18; p = 0.04), while systolic BP change (4 mmHg (-3 - 8)) in HC was not significant (Fig 1A). After HSD, we observed a significant ECV expansion in both CKD and HC subjects (Fig 1B), but no effect on CO. No associations between HSD-induced BP changes and both ECV and CO were found. Systolic BP increase was correlated with SVR decline in HC, but not in CKD patients (Fig 1C). Conclusions: In contrast to healthy persons, BP salt sensitivity in CKD does not associate with vasodilation. Regarding the absence of differences with ECV and CO between healthy and CKD persons, our data indicate that the incapacity for vasodilation might explain salt sensitivity in CKD.

A KETOGENIC DIET REDUCES TISSUE SODIUM CONTENT: AN EXPLORATORY STUDY

Objective: Hypertension and diabetes are a substantial global public health problem. The prevalence of these diseases will further increase in the near future, leading to increased health and socioeconomic costs. Hence efficient therapeutic approaches are urgently needed. It has been previously shown that nutritional approaches including a very-low carbohydrate, or a ketogenic diet potentially decrease body weight, blood pressure and glucose levels in patients with type 2 diabetes along with an overall significant reduction in their pill burden. However, the detailed physiological mechanisms underlying the observed induction and maintenance of diabetes remission remain largely unknown. Previous studies have shown that the skin could be a buffer system for sodium and that skin sodium content could be both a pathogenic cause and a marker of hypertension and salt sensitivity. Since a nutritionally created metabolic milieu such as nutritional ketosis can lower blood pressure, we hypothesize that this dietary approach also reduces tissue sodium content. Design and method: By using 7-T 23Na MRI technique, we performed an exploratory study and analyzed skin and muscle sodium concentration before, and after a 6-week ketogenic diet in three healthy probands. Nutritional ketosis was verified by frequent check of blood ketone (beta-hydroxybutyrate; BOHB) levels greater than 0.3 mmol/L. Results: Preliminary data of our planned exploratory study (in patients with chronic kidney disease and type 2 diabetes mellitus and healthy probands) demonstrated that compared to baseline 6 weeks of ketogenic diet decreased tissue sodium content in the skin (16.6 ± 2.1 vs. 12.6 ± 2.1 mmol/L), in the medial gastrocnemius muscle (20.5 ± 0.9 vs. 16.7 ± 0.7 mmol/L), in the lateral gastrocnemius muscle (19.7 ± 1.0 vs. 16.0 ± 1.0 mmol/L) and in the soleus muscle (13.1 ± 0.8 vs. 11.5 ± 0.5 mmol/L). Conclusions: Our results indicate a massive reduction of tissue sodium concentration in healthy volunteers in response to a ketogenic diet which might be associated with the observed clinical benefits and be implicated in the anti-hypertensive effects of this powerful dietary intervention. Findings of this study could have an impact on future treatment strategies of various chronic diseases.